The impact of the tumor microenvironment on granzyme production by CD8 T cells

Abstract

Granzymes are a class of proteases produced by CD8 T cells to mediate their cytotoxic activity against target cells. The objective of this project is to determine the mechanism through which CD8 T cells are executing their granzyme-mediated cytotoxic function and how the tumor microenvironment (TME) impacts the specific granzymes produced. By micro-array and qPCR we determined that CD8 T cells in the TME have altered expression of specific granzymes. Granzyme F had one of the most altered expressions of all genes examined in antigen-specific CD8 T cells taken from a spleen relative to those taken from a tumor. We further examined the effects of the TME on granzyme expression by sorting tumor infiltrating CD8 T cells on exhaustion markers and found a relationship between exhaustion and granzyme expression, characterized by a decrease in granzyme A and an increase in granzyme B mRNA expression. We will determine the influence different ex vivo culture conditions have on differential granzyme expression and function of CD8 T cells. The expression of different granzymes may have further implications for modulation of the TME through the form of cancer cell death induced, especially the increase in granzyme F which has been suggested to induce a more immunogenic form of cell death. Additionally, the impact of exhaustion on the cytotoxic activity of CD8 T cells from the TME may represent a means for exhausted CD8 T cells to regulate their cytotoxic activity by altering the granzymes they express.